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By T. D. Maki

FMC Gold's Paradise Peak Mine, located 13 km (8 miles) south of Gabbs, Nevada, became operational in April of 1986. Shortly thereafter heap leach testwork began on sub mill grade ore. Presently, testwork continues in combination with production size heaps that account for approximately 6% of total gold production at Paradise Peak.

Jan 1, 1989

By Larry L. Snyder

A compact 4.87 m (16 ft) diameter tunnel boring machine (TBM) is capable of boring a 12.2 m (40 ft) radius curve while gripping horizontally, or vertically, as may be required for the excavation of turnouts. The machine's 5.0 m (16.5 ft) length and a patented machine structure allows steering while boring without causing harmful eccentric loads. An extremely stiff thrust system, rigid front and rear grippers, and the torsional stiffness of a front end electric cutterhead drive combine to create superior machine stability and boring efficiency. A 2.2 m (7.2 ft) diameter prototype, complete with a soft ground shield attachment, was used successfully on a tunnel project in Scotland.

Jan 1, 1989

By Tom L. Enos

Increased production through the plant was limited due to thickener circuit constraints. To overcome these constraints and maximize plant throughput to match grinding circuit capability, two options were considered: A. Adding 2000 TPD CIL circuit to operate in parallel with the existing CCD circuit. B. Adding a CIL circuit to treat the entire 4600 TPD while retaining some thickeners for tailings thickening. Option B was selected based on simplified plant operations, reduced operating costs, minimal capital requirements, reduced solution losses, and bullion grade improvement.

Jan 1, 1989

By R. R. Graham

Echo Bay Minerals operates a 650 tpd gravity float gold circuit at their Manhattan facility. The objective of this paper was to document the gold recovery by size distribution. This was accomplished by studying the material balance of each size fraction as it progressed through each gravity Circuit separator. It proved to be an impossible task. Figure I depicts the gravity circuit. The gravity cyclone underflow goes to two duplex Pan American type jigs. The jig overflow reports to the OK Flash Float Cell. The cyclone hutch product is reground and goes to a full size wilfly table. The rougher table concentrate reports to a pilot size Wi1fly cleaner table. The cleaner and rougher table tails circulate back to the jig feed. The gravity circuit was composite sampled for two to four hours per day for four days. Each sample was taken every 20 minutes. Each composite sample was filtered, dried, repu1ped, and screened through a wet/dry screening procedure. Each size fraction was checked for gold value by fire assay fussion technique. A material balance was run on each size fraction. The tables listing the results are enclosed.

Jan 1, 1989

By Axel J. Pollak

Since the late 1960's the Interstate Division for Baltimore City (IDBC) has been planning and developing the Interstate Highway System for the city to meet regional planning goals. The principal goals are to provide convenient access to the central business district and the port while diverting through traffic away from these congested areas. Interstate Route 95, an eight-lane highway carrying north-south traffic, has headed the city's priority list; during the 1970's its construction proceeded steadily from both east and west towards the harbor. Closing the final 8800-ft (2670-m) gap under the harbor will complete Interstate 95's construction. This final portion, known as the Ft. McHenry Tunnel project, will be built in nine construction contracts. Construction costs of the complete project are expected to exceed $700 million, making it the costliest single project in the Interstate Highway System. Full funding is being provided initially by the Federal Highway Administration (FHWA), and the Maryland Department of Transportation will re-pay the 10 percent local share from toll receipts within the first three years of operation.

Jan 1, 1989

By Mehmet F. Tauer, Pierre Trudel

"The metamorphosed mineralized Archean Bourlamaque batholith, dated at 2710 +-54 Ma, is a homogeneous body, composed mainly of quartz diorite; it is cut by late dioritic, mafic and aplitic dykes, and contains metasomatized ultramafic xenoliths. A geochemical investigation confirms the calc-alkaline affinity of the batholith, and the REE profiles are similar (Lal Yb = 3.9 to 8.1) to those of the intermediate to felsic metavolcanic rocks at Val d'Or into which the batholith was intruded and to those of the calc-alkaline members of the Blake River Group at Rouyn.Gold distribution within the batholith is heterogeneous and anomalous. Although the background Au content of the batholith is estimated to be 3.2 ppb Au by RNAA , the estimated median gold content of the batholith is 10 pp b (with P84 =32 and PI 6=3.1 ppb), much higher than that of ""normal"" granites (I to 5 ppb A u). The gold mineralization exhibits a close relationship with shear zones (e.g. Belmoral Mine) or with diorite dykes (e.g. Sullivan, Perron and Courvan mines).The following sequence of geological events is proposed: (I) pretectonic emplacement of the batholith, which is cogenetic with its volcanic host rocks; (2) regional metam orphism and deformation with localized shearing; and (3) hydrothermal alteration and quartz veining. We conclude that: (1) the Bourlamaque batholith is a gold-enriched intrusion, and (2) the determination of average gold content may be an effective method f or distinguishing ""sterile"" intrusions from those with potentials for gold mineralization.RESUMELe batholite archéen minéralise de Bourlamaque, daté de 2710+-54 Ma, est une intrusion homogène, constituée principalement de diorite quartzique, qui a été recoupée par des dykes tardifs de diorite, d'aplite et de composition mafique. Il contient aussi des enclaves de roches ultramafiques metasomatisees. L 'étude géochimique confirme le caractère calco-alcalin du bath olite et les profits des ETR sont semblables (La/ Yb=3.9 a8.1) a ceux des volcanites intermédiaires afe tsiques de la région de Val d'Or dans lesquelles le batholite fait intrusion et à ceux des unites calco-alcalines du Groupe de Blake Ri ver a Rouyn. La distribution de Au dans le batholite est à la fois anomale et hétérogène. Bien que le bruit de fond du batholite ait été estime à 3.2 ppb A u par AANR, sa médiane a été estimée a10 ppb Au (avec P84=32 et PI6= 3.1 ppb) , ce qui est nettement plus élevé que la valeur des roches granitoides ""normales"" donnée dans la littérature (1 a 5 ppb A u). Dans la batholite, la minéralisation aurifère est intimement associée aux zones de cisaillement (e.g. mine Belmoral) au aux dykes de diorite (e.g. mines Sullivan, Perron et Courvan).La séquence des évènements géologiques suivante est proposée: (1) emplacement pre-tectonique du batholite, lequel est cogenetique avec les roches volcaniques encaissantes; (2) deformation et metamorphisme regional avec des cisaillements tectoniques locaux; et (3) altération hydrothermale et développement des veines de quartz. Nous concluons que: (1) le batho lite de Bourlamaque est une intrusion enrichie en Au; (2) la determination de la teneur en Au peu être une méthode efficace pour distinguer les intrusions stériles de celles qui possèderaient un pot entiel pour des minéralisation s aurifères."

Jan 1, 1989

By Harold Kennedy

Take a good look at this issue of Minerals and Materials. This is the last issue of M&M, as it has been known within the U.S. Bureau of Mines, that you will receive. Fifteen years after it was created to help cope with a growing worldwide mineral shortage, M&M is ceasing publication. In its place will be a bright, new publication called Minerals Today. Like its venerable predecessor, Minerals Today will be a bimonthly magazine that reports on recent trends and issues in the minerals and materials industries. It will be the Bureau of Mines' most frequent periodical presenting an overview of the entire field of minerals and materials.

Jan 1, 1989

"The dust/lung research of the Center has several long-range objectives:* better methods for the early diagnosis of coal workers' pneumoconiosis (CWP);* methods to modify the disease process;* tests to identify toxic products; and* tests to identify individuals with heightened susceptibility to pneumoconiosis.A major immediate objective is to define the mechanism of dust-induced lung disease. This means determining:* dust characteristics that are important in causing lung diseases;* important interactions between dust and lungs; and* earliest detectable stages of the disease.Several of the Center's projects involve exposing lung cells in culture (in vitro) or animal lungs (in vivo) to samples of the suite of characterized mineral dusts described earlier. The responses of the lung cells or tissues to the dusts are being studied in order to better understand how inhaled dusts cause lung disease.One project is studying the effect of dust exposure on the production of mucus by rat tracheal explants in vitro. Mucus is a major factor in clearing inorganic dusts from the lung. Results thus far have shown that exposure of tracheal cultures to coal dust caused a decrease in micin production in comparison to parallel cultures without dust. To examine the effect of in vivo coal dust exposure, rats were maintained in an inhalation chamber for two weeks, and control rats were in an identical, but dust-free chamber. Tracheal explants results indicate that the effect of in vivo dust exposure is similar to that noted in the in vitro experiments.Pulmonary alveolar macrophages (PAMs) are a key component of the lung's response to inhaled particulates, and they play several important roles in pulmonary inflammatory and repair processes. PAMs are the cells that actually ingest dust particles. Other studies have shown that they play a critical role in the development of silicosis and asbestosis. The Center is studying the effect of dust exposure on the release of oxygen free radicals (superoxide) by PAMs. Intercellular production of superoxide occurs when PAMs phagocytize particles, such as inhaled bacteria, and is an essential mechanism by which PAMs kill ingested, bacteria. A number of complex physiological events occur during this process which are not clearly understood. It is thought that PAMs containing indigestible materials, such as mineral dusts, overproduce superoxide, or inappropriately release it into the surrounding tissues. If true, this would cause toxicity to surrounding lung cells by peroxidation of the lipids in the cell membranes. In vitro exposure of PAMs to low or high doses of kaolin is inert. Preliminary studies indicate that coating the quartz particles with a surfactant reduces toxicity."

Nov 1, 1988

"The major thrust of this research is directed towards a better undstanding of the behavior of airborne dust particles in underground mine airways. Figure 61 shows a schematic of dust flow in mine airway. The work included development of a mathematical model of dust behavior in mine airways, experimental study of the behavior of dust clouds and comparison of computer model output and experimental results. Re-entraiment is a secondary source of dust in mine airways and factors affecting re-entrainment are being identified.Investigations have encompassed both experimental and theoretical research into the behavior of dust in mine airways. Experiments were performed in mine airways under both controlled and normal operating conditions (Figure 62). The controlled experiments included the documentation of the concentration and desposition patterns for two types of dust under three different velocities. Real-time dust concentration data were obtained using real-time aerosol monitors (RAM-1) (Figure 63).On the theoretical front, a convection-diffusion model of the dust flow phenomenon in mine airways was developed considering dominant mechanisms affecting dust transport and deposition in mine airways. Mechanisms modeled include turbulent and gravitational deposition, coagulation, and dispersion. Comparative analyses of results of the controlled experiments with the predictions of the mathematical model were carried out. In addition to the overall validity, the adequacy of the individual components of the model, such as deposition in the total and respirable range, and dispersion were examined in light of the experimental observations."

Nov 1, 1988

By Robert A. Jankowski

"Following passage of the Coal Mine Health and Safety Act of 1969 (Public Law 911173), the Bureau of Mines initiated a research program aimed at controlling respirable dust exposures of coal mine workers. Respirable dust is the dust that gets into, and interacts with, the lungs of those who inhale it. It has long been recognized as a severe health hazard to mine workers. This program has been implemented by a team effort consisting of the Bureau's in-house capabilities, the Generic Center for Respirable Dust, and contractors, as necessary. Over the years, Bureau research has addressed principally three areas:o Compliance with the Federal 2.0 mg/m3 dust standard (1970-76).o Dust control for longwall mining (1976-1983).o More stringent respirable dust standards due to quartz dust (1983-1987).In addition, fundamental studies have been conducted by the Generic Center for Respirable Dust, with emphasis on penetration of dust into the lung. Accomplishments have been significant, but problems remain, as noted later.The Coal Mine Health and Safety Act of 1969, established a 2.0 mg/m3 dust standard for all coal mining operations, underground as well as surface. At the time of enactment of this legislation, the industry was averaging approximately 4.0 mg/m3. The Bureau of Mines respirable dust research program played a significant role in identifying and developing effective technology to allow better compliance with this new standard, thanks to industry implementation and Federal enforcement."

Nov 1, 1988

By Carlos Santa Cruz

El presente trabajo refiere los fundamentos teóricos de algunas técnicas de conservación de energía eléctrica dentro de una operación minera como aquellas de control de demanda eléctrica, corrección del factor potencia, utilización de motores de alta eficiencia y control de la iluminación, a fin de enfatizar los beneficios económicos que se puedan obtener de su implementación.

Aug 26, 1988

By Jan M. Mutmansky, Christopher J. Rise

"One of the most serious long term health problems associated with underground,mining is Coal Workers Pneumoconiosis (CWI'), more commonly known as Black Lung Disease. It occurs in some coal workers, normally after 15 or more years of exposure to coal mine dust, and leads to a variety of respiratory problems. Two types of pneumoconiosis are recognized simple CWP, which has been estimated to affect 6.9 percent of miners and is a condition that does not impair the miner's ability to work nor reduce life expectancy; and a more severe form of black lung (called progressive massive fibrosis) that occurs in about one percent of the cases and results in severe lung damage.Although the relationship between coal dust and CWP has long been recognized, detailed knowledge of the relationship is insufficient for setting up authoritative guidelines to reduce the health risks for those employed in dusty,underground environments. CWP is not only a health problem for workers that causes considerable distress, it is also a very expensive problem the total annual costs associated with CWP approach two billion dollars.As part of its efforts to combat CWP, the U.S. Bureau of Mines in 1983 established a Generic Mineral Technology Center to carry out basic research into all aspects of respirable coal dust:— control of dust generation — the behavior of dust in the mine — characterization of dust particles interaction of dust and lung— the relationships among dust generation and mobility and the mine environment, geology, and seam characteristics,Penn State, West Virginia University, the University of Minnesota, and the Massachusetts Institute of Technology are involved in this research, which is administered from the Department of Mineral Engineering at Penn State.Our work is one of the seven projects to be conducted at Penn Slate. We are concerned particularly with the characterization of dust and its relationships with the mine environment, and our main goal is to establish standard procedures for describing and measuring these variables.Coal DustCoal dust is a very complex material that varies greatly in chemical and mineralogical properties. Moreover, it is not the only constituent of respirable dust in the mine. When a coal seam is mined, it is inevitable that rock particles other than coal are included in the material. This rock comes from the mine roof, the floor, and the partings and inclusions within the coal scams. Since the roof and floor strata, the partings and inclusions are often stronger than the coal, mining them frequently causes more dust than mining the coal itself. One of the objectives of our research is to find the relationships between a specific coal's characteristics before it is mined and the respirable dust characteristics after it is mined. We are particularly interested in the size distribution of particles, the chemical properties, and the mineralogical properties."

Jun 1, 1988

By R. V. Ramani, R. Bhaskar

"The control of respirable dust in mines has been given paramount importance due to the health and safety implications associated with fine dust. The understanding of the temporal and spatial behavior of dust has been recognized as essential for increasing the efficiencies of the existing control techniques and for developing new control strategies. Mining-related studies in this area are, in general, limited. They are also mostly experimental. Some mathematical and computer analyses have been attempted. In this paper, first a review of the mathematical studies performed in the last three decades in this area is presented. Second, a mathematical model for analyzing dust flow in mines is proposed. The model takes into account a number of factors affecting dust transport. It incorporates varying dust generation source strengths and dispersion, deposition, and coagulation of dust in mine airways. Finally, application areas for the model are discussed. A computer program based on the mathematical model has been developed. The program will output the dust concentration in the mine atmosphere as a function of time and distance from the source. The amount of dust deposited on the sides, roof, and floor of the airway is also determined.IntroductionAn airborne dust cloud is a complex system containing particles of varied size, density, shape and state of aggregation. The behavior of the particles is dependent on a number of complex physical mechanisms, often opposing in nature. The net interaction results in the ambient concentration. This size dependent behavior of particles contrasts with that of gases, an area quite widely studied.The term aerosol is used to describe clouds of microscopic and submicroscopic particles in air such as chemical smoke or particulate matter released from smoke stacks. An aerosol system can be regarded as an arbitrary element of volume filled with gas and suspended particles of possible highly variable physiochemical nature. The parameters that are used to describe an aerosol system include concentration, mass average velocity and particle mass and radius. In characterizing such systems, several assumptions are made. Among these is the assumption that particles are smooth, inert and rigid spheres. Again, for example, when the particles are in transport, the possibility of collision exists. As a result of the collision, the particles may coalesce to form larger particles. The probability of sticking is considered a known quantity (lady, 1970). In this paper, the application of the principles used in aerosol systems is explored for the study of the transport and deposition of fine coal dust in underground mines."

Jun 1, 1988

By A. Wahab Khair, Nagendra P. Reddy

"This paper presents an analysis of preliminary tests on the effect of in-situ and operating parameters on fragmentation of coal using a specially designed unique automated rotary coal cutting simulator (ARCCS). In these tests coal blocks with an approximate dimension of 18 in. x 15 in. x 6 in. (45.7 cm x 38.l cm x 15.2 cm) were first. subjected to confining pressures, equivalent to in-situ conditions. Such. blocks were then cut by the cutting head of the ARCCS, thus simulating the action of the continuous miner in underground coal mining. During the tests under a particular set of in-situ and operating parameters a number of other parameters such as 1) penetration of bit into coal, 2) penetration resistance (thrust and cutting pressures), 3) rotating velocity of cutting head, and 4) acoustic emission activity in the coal block were monitored. After each cutting cycle the fractured surfaces were photographed and a velocity survey was conducted by using a sonic technique. At the end of each experiment the cutting paths of the bits in coal were photographed using an optical microscope with a camera attached to it. Furthermore, the coal fragments were collected in bags using a vacuum cleaner. These fragments were then sieved for size distribution analysis. The results of the preliminary tests indicated that underground coal cutting can be simulated in the laboratory and the effects of the important parameters, i.e. operating and in-situ parameters, can be studied successfully. INTRODUCTIONThe continuous-mining machines which were introduced in the 1950's now account for more than half the production of coal from underground mines. Unfortunately, these continuous miners, which were designed for increased productivity, have also increased the concentration of respirable dust in mines. As a result, the Federal Coal Mine Health and Safety Act of 1969 was enacted to enforce on the coal operators that the airborne respirable dust not exceed 2 mg/m3, and was intended to reduce the incidence of coal workers pneumoconiosis. This plus the other aspects of the legislation and the subsequent monitoring and enforcement by MSHA made it very imperative that the coal operators provide a relatively healthier and safer working environment for the coal miners. Since 1970, the Federal government has paid over 11.7 billion dollars to more than 470,000 miners with coal workers pneumoconiosis and their survivors (1). These regulations, coupled with the assessment of the continuing burden on miners, the mining industry and taxpayers appear to have provided an impetus for the mining .community towards comprehending the different parameters that influence dust generation and entrainment."

Jun 1, 1988

By A. Wahab Khair

"Geologic materials emit transient noises when stressed /1/. The rate and pattern of these transient noises or acoustic emissions (A.E. hereafter) depend on the stages of deformation of the material /2/. It has been demonstrated that rock/coal fracture processes under stress consist of three distinctive stages--crack initiation, propagation and ultimate fracture--and that coalescence of numerous cracks leads to ultimate failure rather than the propagation of a single crack /2,3/. This paper presents an analysis of fracture formation in rock/coal specimens subjected to straight wedge indentors using A.E. technique.The effect of specimen geometry, wedge indentor angle, confining pressure, and material anisotropy on fracture type (tension, extension, and shear crack), fracture length, and fracture intensity were studied. Two types of material mainly Berea sandstone and Coal Berg No. 2 coal were used in this study. Prior to the experiment the mechanical properties of both sandstone and coal were determined using rectangular specimen (Figures 1 a) in standard compression tests and are given in Table 1. In this study cylindrical and rectangular specimens were first prepared to proper dimensions of 2 in. x 1.5 in. and 3 in. x 1.5 in. x 1.5 in. (5.08 cm x 3.81 cm and 7.62 cm x 3.81 cm x 3.81 cm), respectively and then instrumented with SR-4 strain gages as shown in Figure 1. The instrumented specimens were then tested under four distinct load boundary conditions as illustrated in Figure 2. During a typical experiment the instrumented specimen was placed in a specially designed loading jig (Figure 3) where a predetermined lateral pressure was applied mechanically to the specimen by adjusting the inner plate of the confining chamber via screw while monitoring strains in the specimen. Using rock/coal elastic constants and measured strains, a predeter¬mined lateral pressure was applied to the specimen. Then a vertical load was applied by the straight edge of a wedge indentor attached to the upper platen of the universal loading machine via ball and socket arrangement (Figure 4). The arrangement allowed uniform application of load in a straight line manner on the surface of the specimen. During the test a number of parameters namely strains, load and A.E. rates were recorded (Figures 5a-b)."

Jun 1, 1988

By A. Wahab Khair, Richard D. Begley

"This paper presents results of destructive tests performed on rectangular coal specimen under the influence of two vertical and simultaneous wedge indentation forces. Several wedge designs and spacings were utilized in compression tests. The objective of these experiments was to qualitatively monitor the effect of different wedge designs and spacings on the stress distribution within the coal specimen.Coal samples from the Waynesburg coal seam were cut and trimmed to cubical dimensions of approximately 5 X 10 X 20 cm. These specimen were subjected to parallel compressive forces through two vertically applied wedge indentors. Loading was achieved with a hydraulic hand pump in order to facilitate interferogram construction. The load increments were limited due to the sensitivity of the holographic interferometric technique (holometry) in measuring small displacements; therefore, interferograms were taken only during similar increments in order to allow for a qualitative comparison between different wedge design and spacings. In some cases, interferograms were taken immediately before and after failure of the specimen.Introduction Failure Modes Three distinct modes of failure occur when geologic materials are subjected to wedge indentation forces. As shown in Figure 1, a crushed zone is located immediately adjacent to the indentor while chipping can occur if the fractures initiated in the crushed zone extend upwards to the free surface.. The third failure mode is a zone of intricate frac¬tures located between the crushed zone and the chipping zone. Several experiments have been conducted over the years to better understand crater formation and stress distribution within geologic materials under the influence of an indentor. Generally speaking, crack initiation and propogation observed in these experi¬ments correlate fairly well with wedge indentation theory; however, the nature of the .fractures is greatly influenced by different material properties such as grain size and cleavage planes. In other words, a wide range of behavior has been found in different rocks subjected to wedge penetration. For example, it has been observed that some rocks are merely crushed and indented while others are more prone to cracking and chip formation. Therefore, the development or nondevelopment of chips depends mostly on wedge geometry, rock type and depth of penetration. This work is part of the study associated with opti¬mization of cutting parameters, which is best modeled by using brittle materials and subjecting them to rigid wedge penetration tests."

Jun 1, 1988

By A. Wahab Khair, W. M. Devilder

"This paper presents an analysis of fragment size distribution and characteristics of fracture surface in coal cutting using a rotary coal cutting simulator. Coal cutting by a drum type continuous miner was simulated in the laboratory. A series of tests along both the face and butt cleat direction of coal under different operating and in-situ conditions were performed. In each experiment the cut surface was photographed microscopically and the coal cuttings were collected and sized. Data were used to show how and to what extent various parameters effect size distribution of the coal cutting and how this correlates with the characteristics of the fracture surface. This study resulted in establishing a number of distinct correlations between the size distribution and fracture surface. These correlations were primarily based on the degree of interaction between adjacent bits and the amount of bit-coal interaction taking place on the cutting path. Some of the major results of this study are as follows:Zones of bit-coal interactions proved vital toward understanding the effect the conical bit has on the fragmentation process. This in turn led to the identification of areas which are responsible for the production of fines and generation of respirable dust.The various parameters employed in the coal cutting experiments which showed a strong effect on the coal fragment size distribution were: bit type, bit spacing, depth of cut, in-situ stresses, and cleat orientation. Bit angle and cutting head velocity exhibited the least effect and no correlation was established.From this study it is obvious that the key to achieving efficient coal fragmentation is to limit the degree of bit-coal interaction that takes place throughout the bit path while causing maximum interaction between adjacent bits. Accomplishing this not only increases the percentage of large fragments produced but limits the amount of secondary crushing that takes place in the bit path thus resulting in decreasing fines and consequently, the amount of respirable dust generated.Over 2,000 continuous mining machines (introduced in the 1950's) equipped with conical bits or point attach bits account for well over half of the United States' production from underground coal mines. Today, competition in the coal industry has increased, due mainly to coal market conditions and legal restrictions, thus placing an emphasis upon increasing production, efficiency and health/safety of the workers. Mine operators are always interested in finding the most efficient performance of continuous mining machinery to produce the largest amount of size of coal at the lowest cost. An increase of fine material sent to the cleaning plant can seriously overload the plant to the extent that plant efficiencies deteriorate significantly (1). Also, the difficulty and expense of cleaning very small particles often cannot be done economically and thus, thousands of tons of coal are sent to the refuse pile because of costly or ineffective cleaning facilities. It has been said, ""the efficient extraction of coal or rock implies breakage into a size range that contains a minimum quantity of very small sizes"" (2). All known fragmentation theories concur that more fragmentation requires more energy (3). So, the importance of reducing fines is already evident from an outlook upon efficiency.Now, let's consider another view point., duet generation."

Jun 1, 1988

By D. Hinton, M. McCawley, R. C. Lantz, F. Pisano, C. Stanley

"INTRODUCTION Aerosols (5 um have not been shown to be consistently generated and characterized in inhalation chambers. Particle deposition in the lungs however may occur with particles as large as 25 um(1). Therefore, in order to closely simulate the atmosphere of an underground coal mine where the distribution is bimodal, with modes at S and 15 um (2), particles much greater than <1 um must be characterized for uniform mixing and size distribution within these chambers. The Hazelton Animal Exposure Chamber has been chosen because it has been best characterized for smaller particles (<1 um) (3), and is the major type used by most inhalation toxicology institutes such as Lovelace Inhalation Toxicology Institute and Battelle Northwest Laboratory.BACKGROUNDPreviously published studies on the inhalation of solid aerosols have attempted to characterize the distrition of particles of <2 um in diameter. There are no published reports of extensive work characterizing either the size distribution of particles <1 um or the concentration throughout the exposure chamber (Table 1).Table 1 shows the variability and sizes of several aerosols <1 um in diameter used in five previous chamber studies.Discussion of Previous StudiesThe study done by Bauermash, Bryan, Dickinson, and Burke (4)stated two major concerns in the development of the 6.5 ft. diameter chamber. The first was that a quantity of animals could be exposed to the same concentration regardless of the location of the animal, and second was that the chamber could be easily cleaned and decontaminated. The solution to the first concern required a circular chamber with the contamination air entering the chamber somewhere along the central axis. The animals could then be changed during exposure time so that each animal was exposed throughout the total volume."

Jun 1, 1988

By W. E. Wallace, V. Robinson, M. F. Keane, V. Vallyathan

"An in vitro study of the biologic responses of surface-modified and native silica and kaolin was made to provide comparative information on the supression of cytotoxicity by pulmonary surfactant. The release of alveolar macrophage cytoplasmic enzyme, lactate dehydrogenase (IDH), and lysosomal enzymes B-N-acetylglocosaminidase (B-NAG) and B-ghucuronidase (B-GLUC) and sheep blood-cell hemolysis were moni¬tored as indicators of cell membrane damage and cytutoxicity. Surface modification of silica and kaolin with dipalmitoyl lecithin (UPI) resulted in complete abrogation of cytotoxicity of both minerals. These findings indicate that surface modification of minerals with different adsorption properties by pulmonary surfactant generally lessens their prompt adverse effects.INTRODUCTIONAcute and chronic silicosis are well-characterized clinical and pathologic entities resulting from the inhalation of crystalline silica (Morgan and Seaton, 1984). Kaolin, a layered aluminosilicate clay frequently mined and used in manufacturing, contains tetrahedral silica alternately layered with alumina octahedra. Kaolin is relatively .inert biologically, and distinctly greater pulmonary burdens are seen in patients with kaolinosis than are seen in patients with silicosis. Crystalline siliea (quartz) induces a significantly greater degree of fibrosis in exposed animals in vivo than does kaolin (Hamilton and Hardy, 1974; Parkes, 1982; Hunter, 1976; Sheers, 1964; Warraki and t-lerant, 1963; Lynch and Mciver, 1954; Lapenas et al., 1984).This difference in pulmonary disease associated with the two types of dust is not reflected by in vitro cytotoxicity as Jetermined by pulmonary macrophage bioassays or erythrocyte hemolysis. Cytotoxicity studies using crystalline silica and kaolin of similar size fractions show comparable bioassay response on a mass basis. These cellular bioassays, therefore, do not correlate with the relative in vivo pathogenicity of silicates."

Jun 1, 1988

By M. K. Quinn, A. W. Khair

"This paper presents an analysis of respiraple dust generation due to the action of a continuous miner. Underground coal cutting by a drum-type continuous miner was simulated in the laboratory using a specially designed unique automated rotary coal cutting simulator (ARCCS). An analysis of -400 mesh particles was done on gravity collected material. Samples of entrained dust were collected through the use of cascade impactors. Both samples were analyzed for size distribution and particle shape. Using the simulated coal cutter permitted variation of operating and in-situ parameters to provide information on the effects on generation of -400 mesh particles. In these tests coal blocks with an approximate dimension of 18 in. x 15 in. x 6 in. (45.7 cm x 38.1 cm x 15.2 cm) were first subjected to confining pressures, equivalent to in-situ conditions. Such blocks were then cut by the cutting head of the ARCCS, thus simulating the action of the continuous miner in underground coal mining. During the tests under a particular set of in-situ and operating parameters a number of other parameters such as 1) penetration of bit into coal, 2) penetration resistance (thrust and cutting pressures), 3) rotating velocity of cutting head, and 4) acoustic emission activity in the coal block were monitored. After each cutting cycle the fractured surfaces were photo¬graphed and a velocity survey was conducted by using a sonic technique. At the end of each experiment the cutting paths of the bits in coal were photographed using an optical microscope with an attached camera.IntroductionThe continuous-mining machines introduced in the 1950's now account for more than half the production of coal from underground mines. Unfortunately, these continuous miners, designed for increased productivity, have also increased the concentration of respirable dust in mines. As a result, the Federal Coal sine Health and Safety Act of 1969 was enacted to enforce on the coal operators that the airborne respirable dust not exceed 2 mg/m3, and was intended to reduce the incidence of coal workers pneumo-coniosis. This plus the other aspects of the legislation and the subsequent monitoring and enforcement by MSHA made it very imperative that the coal operators provide a relatively healthier and safer working environment for the coal miners. Since 1970, the Federal government has paid over 11.7 billion dollars to more than 470,000 miners with coal workers pneumoconiosis and their survivors (Newmeyer, 1981). These regulations, coupled with the assessment of the continuing burden on miners, the mining industry and taxpayers appear to have provided an impetus for the mining community towards comprehending the different parameters that influence dust generation and entrainment."

Jun 1, 1988